This invention relates to a method of fabricating a cold cathode for field emission, more particularly, to a method of fabricating a cold cathode having a sharp emitter.
In general, it is known that a cold cathode has an emitter which emits electrons by field effect. The cold cathode may be used in a key device in vacuum microelectronics.
On fabricating the cold cathode, silicon is used since fine patterns may be easily formed with high precision. A conventional method is disclosed in Japanese Patent Publication Tokkai Hei 5-94762 (94762/1993).
The conventional method comprises a step of etching silicon substrate by isotropic etching to form a sharp emitter on the silicon substrate. The sharp emitter has a cone shape. Inasmuch as the isotropic etching is used in the conventional method on forming the sharp emitter on the silicon substrate, it is difficult to control an etching time for sharp emitter in the conventional method. In order to easily control the etching time for the sharp emitter, an improved method is disclosed in Japanese Patent Publication Tokkai Hei 3-95829 (95829/1991) and will be referred to as a first conventional method. Oxidation is used in the first conventional method on forming the sharp emitter on the silicon substrate.
Furthermore, another improved method is disclosed in "New Structure Si Field Emitter Arrays with Low Operation Voltage" which is published in International Electron Device Meeting (IEDM), 1994, pages 23 to 26 and will be referred to as a second conventional method. Anisotropic etching is used in the second conventional method on forming the sharp emitter on the silicon substrate.
However, it is difficult to make the sharpness of the emitter be good in the first conventional method inasmuch as oxidation is used in the first conventional method on forming the sharp emitter on the silicon substrate. Furthermore, it is difficult to control the height of the sharp emitter at a high accuracy in the first conventional method. As a result, it is difficult to stably form the sharp emitter on the silicon substrate in the first conventional method.
Similarly, it is difficult to stably form the sharp emitter on the silicon substrate in the second conventional method as will be later described.